The invention relates to communications in general. More particularly, the invention relates to a method and apparatus for measuring multicast performance over a network, such as a high performance Internet Protocol backbone network.
The services available over communication networks in general, and the Internet in particular, are growing at an exponential rate. It seems that every day a new application is introduced that makes it more convenient to transact business or enhance the accessibility of information to the individual user. As these services and applications develop, however, an increasing pressure is exerted on the limited resources of conventional networks such as the Internet. Bandwidth and scalability become limiting factors to the introduction and delivery of these new services. Consequently, communications technologies are continually evolving in response to these constraints.
High performance networks are currently in development and directly address this demand. For example, a high-speed research and education network is currently under development by a group co-sponsored by the United States National Science Foundation (NSF) and MCI WorldCom. This network is referred to as the very high speed Backbone Network Service (vBNS). The vBNS network was chartered in 1995 to serve as a proving ground for new technologies, to support the development of advanced services, and to support the research conducted by its user community. Currently, the vBNS is implemented as an IP-over-ATM network, that is, its Network Layer (Layer 3 of the Open Systems Interconnection reference model promulgated by the International Organization for Standardization) runs the Internet Protocol (IP) on top of the Asynchronous Transfer Mode (ATM) protocol. Those protocols, in turn, run on a Synchronous Optical Network (Sonet) 622 Megabits per second (Mbps) infrastructure.
One advanced network service that is currently being tested for deployment over the vBNS is the IP multicast delivery service (the xe2x80x9cmulticast protocolxe2x80x9d or xe2x80x9cIP multicastxe2x80x9d). The multicast protocol service at the IP layer enables a data source to use a group address to send an IP datagram to a set of receiving end-systems. The service, provided by the network, delivers the packet to all members of the group. In this manner, the network is responsible for intelligently replicating a packet such that all intended receivers receive the packet. By way of contrast, the traditional unicast service model has a single end-system send a packet to exactly one receiving end-system.
The implementation and refinement of the multicast protocol over the vBNS network is highly desirable for a number of reasons. The vBNS maintains a native IP multicast service, meaning the network is capable of routing and delivering IP multicast packets without tunneling. This removes the need for dedicated multicast routers and their attendant inefficiencies. The vBNS uses a protocol-independent multicast (PIM) dense-mode configuration among all vBNS routers. Distance vector multicast routing protocol (DVMRP) unicast routing is used, allowing the vBNS to support delivery of multicast backbone (Mbone) traffic. The Mbone is an experimental network that is built, using tunnels, over the commodity Internet. Potential multicast applications include communication between World Wide Web (WWW) caches, videoconferencing, MBone sessions, and updates from personal computer (PC) based traffic-measuring devices used to monitor network performance (e.g., xe2x80x9cOC12MONxe2x80x9d discussed later).
One problem associated with deployment of IP multicast over a high speed network such as vBNS is the absence of a robust measurement tool to assist in the deployment of the multicast protocol. Current testing protocols focus on measuring performance of the IP unicast protocol. Conventional unicast performance measurement protocols, however, do not translate well for use with measuring multicast performance, including loss packet rate and data rate. For example, conventional unicast performance measuring protocols implemented on the vBNS are typically based on carefully timed xe2x80x9ccronxe2x80x9d jobs. In other words, if a network comprises ten network nodes, each node will begin executing a test run of packets at a predetermined time in sequence. Thus, node 1 may be instructed to send one hundred thousand packets to node 2 at a predetermined time. Node 2 will count the number of packets received from node 1 and at what rate (e.g., 90,000 received at 4.98 megabits per second (Mbps)). By way of contrast, multicast testing requires a single node sending the same information to multiple receiving nodes. This type of testing requires more coordination than the simple one to one transfer of information. In another example, conventional testing protocols are limited in terms of the type of information measured. The conventional testing protocols fail to gather any information regarding the loss pattern of the packets not received or received out of sequence. Furthermore, since there is only one data sender and multiple data receivers, there exists a need for compiling the loss patterns across multiple receivers to compare performance and help identify potential loss conditions.
In view of the foregoing, it can be appreciated that a substantial need exists for a method and apparatus for measuring multicast performance over a network that solves the above-discussed problems.
One embodiment of the invention comprises a method and apparatus to measure multicast performance over a network. A data coordinator coordinates a multicast protocol test between a data sender and a plurality of data receivers. The dalta coordinator receives a test report from each of the data receivers. The data coordinator prepares a loss report using the test reports.
With these and other advantages and features of the invention that will become hereinafter apparent, the nature of the invention may be more clearly understood by reference to the following detailed description of the invention, the appended claims and to the several drawings attached herein.